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[Joachim De Lombaert <question147846@xxxxxxxxxxxxxxxxxxxxx>]

Question #147846 on Graphite changed:
https://answers.launchpad.net/graphite/+question/147846

Description changed to:
Hi,

We're measuring a metric whose values can vary greatly over short spans
of time. I'm trying to smooth out the data using the movingAverage
function to get a better visualization of the general trend, since the
10s realtime data is too noisy. I've built a graph that shows the raw
data and the 1min, 10 min, and 1 hour moving averages:

alias(sumSeries(fish.eaten),"metric")
alias(movingAverage(sumSeries(fish.eaten),6),"1min avg")
alias(movingAverage(sumSeries(fish.eaten),60),"10min avg")
alias(movingAverage(sumSeries(fish.eaten),360),"1h avg")

We've only gathered about 36 hours of data so far. Plotting this data on
a graph for the past 36 hours works well. The problem we're having
occurs whenever we set the date range to over 36 hours (past the point
at which we started collecting data). In those cases, the plots for the
moving average lines do not scale along the x-axis in the same way as
the plot for the realtime metrics data. So if we were to set the date
range to 100 hours, only the last 36 of those would show real-time data,
but the movingAverage plot would still show non-zero data for most if
not all of those 100 hours.

This is easiest to explain with examples.

http://external.pcheese.net/bugs/graphite/moving-average-x-shift.png
- Two separate graphs of the same data (listed above), at different date ranges.
- Top graph has a 36 hour date range, and everything looks OK.
- Bottom graph has a 48 hour date range, and the peaks in the movingAverage plots do not correspond to those 
- I've added lines that show how a single corresponding peak in the 36 hour graph splits into two separate peaks in the 48 hour graph. 

http://external.pcheese.net/bugs/graphite/moving-average-x-shift-360hrs.png
- Single graph of the same data (listed above), with a date range of 360 hours

As you can see, the moving average does not seem to be plotted correctly
along the X axis.

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